System for the conversion of microwave energy into electric direct current energy utilizing an electron beam tube

ABSTRACT

1,146,444. Velocity-modulated tubes. SIEMENS A.G. 14 April, 1966 [15 April, 1965], No. 16296/66. Heading HID. In a microwave/D.C. converter, the microwave signal produces a uniform increase in the drift velocity of an electron beam, the subsequent retardation of which by a gridded collector system provides the D.C. output. In one embodiment (Fig. 1, not shown), the microwave signal is applied to a Cuccia coupler to produce a fast cyclotron wave on an electron beam moving in an axial magnetic field, the cyclotron wave being subsequently converted to a synchronous wave-with a consequent uniform increase in the drift velocity of the beamby an abrupt reversal in sense of the magnetic field. Instead of a Cuccia coupler, a waveguide providing a circularly polarized electric field may be employed. In another embodiment, Fig. 3, which dispenses with a magnetic field, the coupler is in the form of a pair of parallel electrodes twisted about the beam to impose upon the latter a continuous radial deflection, such that the resultant beam rotates around a conical surface, the collector 5 with its grid 6 being of appropriately concave shape to ensure normal receipt of the beam. The coupler in this embodiment may be in the form of a twisted rectangular waveguide (Fig. 4, not shown), arranged such that during a half-cycle of the microwave signal, the beam traverses a 180 degree section of twist.

Aug. 19, 1969 H. SEUNIK ETAL 3,462,636

SYSTEM FOR THE CONVERSION OF MICROWAVE ENERGY INTO ELECTRIC DIRECT CURRENT ENERGY UTILIZING AN ELECTRON BEAM 'ruam Filed April 6, 1966 MAGNETIC GENERATING MEANS J Fig.2

INVENTORS .S a z N MW Zn 5 n e 7:. Mm W a m .B

United States Patent 96,63 Int. Cl. HOlj 23/16, 29/96 US. Cl. 315--3 6 Claims The invention relates to a system for the conversion of microwave energy into electrical direct current energy by means of an electron beam tube which contains a coupling structure for the coupling of the microwave energy onto the electron beam and a device for the braking of the electron beam carrying the microwave energy.

For some time, work has been going on on the problem of achieving a wireless energy transmission with the aid of microwaves. The wireless transmission of high powers is of considerable importance especially for the supply of energy to flying bodies. An energy transmission by means of microwaves, however, can also be important in transmission over great distances on earth.

In experiments heretofore known in the transmission of high powers with the aid of microwaves there have been utilized, among other things, for the rectification of the microwave energy an electrostatically focused klystron tube. The electron beam of the klystron is in this case modulated with the microwave energy and, by braking the electron beam, a part of the microwave power is thereby converted into direct (non-alternating) energy. A velocity-modulated electron beam such as occurs, as is well known in klystrons, presents, of course, a longitudinal velocity distribution, so that the efficiency of the conversion of microwave energy into direct energy is thereby limited from the outset.

The invention has as its underlying problem that of creating a system for the conversion of microwave energy into direct energy with the aid of an electron beam tube, whose efliciency is not limited by a longitudinal velocity distribution of the beam electrons. For the solution of this problem, it is proposed, according to the invention, in a system of the type initially mentioned, that the coupling structure of the electron beam tube be constructed as a coupler in which the electrons of the electron beam undergo, in addition to their movement in electron beam direction, a radial deflection out of the axis of the unmodulated electron beam, in which process the deflection of the electron beam is converted into a uniform increase of the drift velocity of the electrons.

A system according to the invention has the advantage that in the coupling of the microwave energy onto the electron beam there occurs substantially no longitudinal velocity distribution. The deflection imparted to the electron beam out of the beam axis is expressed either directly in a uniform increasing of the drift velocity of the electron or is converted into a corresponding velocity increase. As a result, all of the electrons of the electron beam can be uniformly braked, so that the entire energy conducted by the beam is recovered in the form of direct current power. The efiiciency of the system depends essentially only on the losses in the coupler and can, therefore, attain values of over 90%.

An electron beam which travels in a stationary homogeneous magnetic field extending longitudinally with respect to the electron beam direction, as is well known, is modulated with so-called transverse waves when a high frequency field directed transversely to the electron beam Patented Aug. 19, 1969 axis acts on the electron beam. The electron beam tube of a system according to the invention can operate with such transverse waves, in which case expediently there is first generated in the electron beam a rapid cyclotron wave which is transformed by a reversal of the magnetic field strength direction into a synchronous wave.

Instead of a modulation with the known transverse waves, the electron beam tube of a system according to the invention can also be operated purely electrostatically, without a magnetic field. It is necessary in this case that the coupler for the microwave energy be so constructed that the electrons of the electron beam receive an additional energy in radial direction. The electron beam then rotates as a whole in a conical pattern. Care must be taken, however, that the braking direction agrees with the direction of the individual diverging electron paths. This can be achieved in simple manner by an arrangement in which the braking electrode has a surface which is curved concavely with respect to the arriving beam.

The invention will be explained in detail with the aid of the examples of construction illustrated in the drawing, wherein like reference characters indicate like or corresponding parts, and in which:

FIG. 1 illustrates schematically a longitudinal sectional view of elements of an electron system tube embodying the invention;

FIG. 2 is a graph illustrating the course of the magnetic field along the tube axis and is vertically oriented with FIG. 1 to indicate the magnitude of the magnetic field at corresponding points along the tube axis;

FIG. 3 is a schematic view, similar to FIG. 1, illustrating an electron system, embodying the invention, which does not require a magnetic field; and

FIG. 4 illustrates a part of a coupling portion which is suitable for use in the arrangement of FIG. 3.

Referring to FIG. 1, an electron beam generation system, comprising a cathode 1 and focusing electrodes 2, generates an electron beam 3, which beam passes through a coupling portion 4 charged with high frequency energy HF. Following the coupling structure 4 is a catcher electrode 5, provided with a grid 6 at which the electron beam is braked. The coupling structure 4 advantageously is a so-called Cuccia coupler. Such a coupler consists, in the simplest case, of two electrodes extending in electron beam direction parallel to the beam axis, to which electrodes the high frequency energy HF is so supplied that it forms between said electrodes a linearly polarized transverse electric field. The frequency of the high frequency energy should correspond substantially to the frequency generally designated as cyclotron frequency of the electrons in the magnetic field B (FIG. 2) which is present at the location of the coupler. The Cuccia coupler then generates in the electron beam a cyclotron wave of positive energy which is expressed in that to the electrons of the electron beam, with constant movement in electron beam direction, there is fed a rotary energy which corresponds to the coupled-in microwave energy. Such cyclotron wave is thereupon transformed into a rapid synchronous wave by a directional reversal of the magnetic field B This magnetic field reversal theoretically is to be made particularly abrupt. In practice, however, it is sufficient that the reversal length be short as compared to the cyclotron wavelength. The conversion of the cyclotron wavelength into a synchronous wave means that the rotational energy of the electrons is converted into an increase in the longitudinal velocity of the electrons. (An example of a synchronous wave is, as is well known, an electron beam whose electrons travel straight ahead and which as a whole rotates on its axis.) On the grid 6 of the catcher electrode 5, therefore, the electrons of the electron beam can be uniformly braked to zero, so that the high frequency energy supplied to the electron beam is practically completely recovered, along with the energy imparted to the beam in the beam generator, on resistor 7 as rectified power.

The use of a Cuccia coupler has the advantage that no appreciable longitudinal velocity distribution occurs in the electron beam even if the latter has a very great cross section. On the other hand, in the Cuccia coupler there exists the strict relation between signal frequency and cyclotron frequency. When it is desired to utilize a lower magnetic field it is possible to use instead of the Cuccia coupler, any other known transverse wave coupler. In particular there comes under consideration as a coupling structure for a rapid cyclotron wave a coupler which conducts a high-frequency electric field directed transversely to the electron beam axis, with such field being circularly polarized. The circular polarization of the electric alternating field is necessary in order to achieve a cyclotron wave with only positive energy.

FIG. 3 schematcially illustrates an example of construction embodying invention, in which the electron beam tube operates without a magnet field. By reason of the absence of the magnetic field, the terms cyclotron wave and synchronous wave are not applicable in this case. Nevertheless, it is possible to achieve, as with the known transverse wave couplers, a modulation of the electron beam 3 with high frequency energy without having imparted to it a longitudinal velocity distribution. To achieve this it is proposed that the coupling structure 4 contain two electrodes parallel to one another, to which the high frequency energy is supplied in the same manner as in the Cuccia coupler and which electrodes are continuously entwined with one another in electron beam direction whereby the electrons undergo, in addition to their movement in electron beam direction, a radial deflection out of the beam axis. Such a coupling between the high frequency energy and the electron beam has the effect that the beam as a whole rotates in a conical pattern. In order to transform the energy of the electrons into a direct electrical voltage it is then necessary that the braking electrode 5, 6 form a surface which is curved with respect to the incoming beam. For example, in the form of construction illustrated the catcher 5 and the braking electrode 6 are in the form of a spherical shell. The braking electrode 6 is in this case disposed as close as possible to the coupling portion, because, in the absence of a magnetic conduction field, the electron beam diverges substantially after leaving the coupler.

For the coupling structure of the embodiment represented in FIG. 3 there is especially well suited a construction such as that illustrated in FIG. 4, comprising a hollow conductor of rectangular cross section which is twisted in electron beam direction. The twisting is to be so selected that the electrons undergo a continuous radial deflection out of the beam axis. During a half cycle of the high frequency oscillation which is supplied to the coupling portion, the electrons must pass through a twisting of 180. The twisted hollow conductor expediently has resonance characteristics, its length amounting to about a half wavelength of the high frequency oscillation. The production of the twisted hollow conductor illustrated in FIG. 4 can be accomplished, for example, by the method of filling a straight hollow conductor made of copper with sand or the like and then twisting it into a screw-like formation. Another method of manufacture would be to twist a tin bar of rectangular cross section into a screw-like formation and then cover it with copper by means of an electrolytic bath, following which the coupler may be obtained by chemically dissolving the tin mandrel.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

We claim as our invention:

1. An arrangement for the conversion of microwave energy into electrical DC energy by means of an electron beam tube, comprising means for generating an electron beam traveling along an axis, means to which the microwave energy is to be applied, disposed to act on such electron beam for effecting a coupling therebetween by means of which such microwave energy is impressed on the electron beam, said means being so constructed that the electrons undergo, in addition to their movement in axial direction, a radial deflection out of the beam axis, without imparting to the electron beam any material velocity distribution, an electrode disposed in the path of said beam, following exit thereof from said means, for braking the electron beam carrying the microwave energy, and a catcher electrode disposed in the path of the electron beam, immediately following the exit of the electrons from said braking electrode, at which the braked electrons are collected, and which forms the output electrode at which the energy originally imparted to the beam is recovered as direct current energy.

2. An arrangement according to claim 1, wherein said means is constructed to form a coupler for a fast cyclotron wave, and includes means for generating a longitudinally extending homogeneous magnetic field oriented in electron beam direction which makes a reversal of the magnetic field strength direction intermediate the coupler and the catcher, whereby the cyclotron wave is converted into a synchronous wave.

3. An arrangement according to claim 1, wherein the electron beam tube operates electrostatically, said means comprising two uniformly spaced electrodes extending in the direction of the electron beam and continuously twisted with each other, the braking electrode having a concave curved surface facing the incoming beam, and the catcher having a similar configuration.

4. An arrangement according to claim 2 wherein the cyclotron wave coupler is a Cuccia coupler with resonant properties.

5. An arrangement according to claim 2, wherein the cyclotron wave coupler consists of a wave conductor which has an electrical field oriented transversely to the electron beam axis, and said electrical field is polarized circularly.

6. An arrangement according to claim 3, wherein the coupling member is a twisted hollow conductor of rectangular cross-section and the braking electrode is arranged immediately behind it relative to the beam direction.

References Cited UNITED STATES PATENTS 2,638,561 5/1953 Sziklai 33225 X 3,085,189 4/1963 Thonemann et a1. 32132 3,122,710 2/1964 Miller 330-4.7 3,189,750 6/1965 Dain et a1. 32165 X 3,218,503 11/1965 Adler 330--4.7 X

HERMAN KARL SAALBACH, Primary Examiner S. CHATMON, JR., Assistant Examiner US. Cl. X.R. 

1. AN ARRANGEMENT FOR THE CONVERSION OF MICROWAVE ENERGY INTO ELECTRICAL DC ENERGY BY MEANS OR AN ELECTRON BEAM TUBE, COMPRISING MEANS FOR GENERATING AN ELECTRON BEAM TRAVELING ALONG AN AXIS, MEANS TO WHICH THE MICROWAVE ENERGY IS TO BE APPLIED, DISPOSED TO ACT ON SUCH ELECTRON BEAM FOR EFFECTING A COUPLING THEREBETWEEN BY MEANS OF WHICH SUCH MICROWAVE ENERGY IS IMPRESSED ON THE ELECTRON BEAM, SAID MEANS BEING SO CONSTRUCTED THAT THE ELECTRONS UNDERGO, IN ADDITION TO THEIR MOVEMENT IN AXIAL DIRECTION, A RADIAL DEFLECTION OUT OF THE BEAM AXIS, WITHOUT IMPARTING TO THE ELECTRON BEAM ANY MATERIAL VELOCITY DISTRIBUTION, AN ELECTRODE DISPOSED IN THE PATH OF SAID BEAM, FOLLOWING EXIT THEREOF FROM SAID MEANS, FOR BRAKING THE ELECTRON BEAM CARRYING THE MICROWAVE ENERGY, AND A CATCHER ELECTRODE DISPOSED INTHE PATH OF THE ELECTRON BEAM, IMMEDIATELY FOLLOWING THE EXIT OF THE ELECTRONS FROM SAID BRAKING ELECTRODE, AT WHICH THE BRAKED ELECTRONS ARE COLLECTED, AND WHICH FORMS THE OUTPUT ELECTRODE AT WHICH THE ENERGY ORIGINALLY IMPARTED TO THE BEAM IS RECOVERED AS DIRECT CURRENT ENERGY. 